The present invention relates to a secure integrated circuit device comprising, firstly, an active layer made up of a semiconductor material and of circuits integrated into said semiconductor material and having contact tabs on its active face and, secondly, an additional layer. The present invention also relates to a method of manufacturing such a device.
The invention is generally applicable to the field of integrated circuits and, more particularly but in non limiting manner, to the field of portable objects having integrated circuits and of the format of a memory card or cards.
As currently made, a memory card commonly comprises a card body made of a plastics material and provided with a cavity in which an electronic module is inserted. The module comprises an integrated circuit and a support for said integrated circuit. When the card operates using contacts, the integrated circuit is connected to regions of the support of the electronic module that are flush with the surface of the card body and, when the card operates without contacts, the integrated circuit is connected to the terminals of an antenna.
Such memory cards are designed for performing various operations such as, for example, payment operations associated with obtaining encrypted television channels, operations associated with the healthcare field, debit operations in public transport vehicles, telephony operations, or banking operations. Such operations are performed in read mode or in read/write mode by means of electrical or electromagnetic coupling between the electronic module of the card and a reader.
In order to avoid or at least limit fraud and/or breaches of civil liberties (e.g., access to personal confidential data stored in the memory card) many different means have been developed. In particular, such means include secret codes, encrypting or authentication keys, or conversion tables. In cards having microcontrollers, such means, as well as the secret information contained in the chip, are essentially contained in Electrically Erasable Programmable Read-Only Memories (EEPROMs) and in Read-Only Memories (ROMs) of the chip, which memories are managed by a Central Processing Unit (CPU).
It is sometimes possible to access secret information contained in the chip by physically analyzing the integrated circuits that it contains.
That is why various techniques have been developed for the purpose of making the integrated circuits secure.
Some of such techniques consist in covering the surface of the integrated circuit, in particular the surfaces of the memory planes of said circuit, with layers of polymer and of metal. The maze-like and entangled nature of the layers makes it difficult to recognize the actual layout of the circuit.
Unfortunately, the degree of security obtained by means of such techniques is not absolute because it sometimes remains possible to access the circuits and the information contained therein by successively and selectively subjecting various layers to chemical etching.
Other techniques propose placing a second, xe2x80x9cslavexe2x80x9d integrated circuit above a xe2x80x9cmasterxe2x80x9d integrated circuit to be protected, and interconnecting said integrated circuits so that if they are separated, then, for example, the secure data is lost irreversibly. Such a device, as described in U.S. Pat. No. 5,877,547, is effective in applications in which said device is always switched on.
Given the above, an object of the invention is to limit the possibilities of physical access to the integrated circuit of an integrated circuit device at lower cost and more effectively, and without requiring the device to be powered continuously.
This and other objects are attained in accordance with one aspect of the present invention directed to a secure integrated circuit device comprising firstly an active layer made up of a semiconductor material and of circuits integrated into said semiconductor material and having contact tabs on its active face, and secondly an additional layer, active layer is bonded to the additional layer by an intermediate layer applied to the surface of the active face of the active layer, and the face of the active layer opposite from its active face is thinned.
Another aspect of the invention is directed to a method of manufacturing a secure integrated circuit device comprising firstly an active layer made up of a semiconductor material and of circuits integrated into said semiconductor material and having contact tabs on its active face, and secondly an additional layer, active layer is bonded to the additional layer by an intermediate layer applied to the surface of the active face of the active layer, and the face of the active layer opposite from its active face is thinned.
A secure integrated circuit device is thus obtained by making recovery of the active face by physical intrusion critical. In addition, the thickness of the assembly made up of the active layer and of the additional layer, i.e. thickness of the secure integrated circuit device, is about the same as that of a conventional, non-secure integrated circuit device.